#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
#include <stdlib.h>
#include <time.h>

struct TreeNode 
{
    int val;
    struct TreeNode* left;
    struct TreeNode* right;
};

int maxDepth(struct TreeNode* root)
{
    if (root == NULL)
        return 0;

    return fmax(maxDepth(root->left), maxDepth(root->right)) + 1;
}